Curiosity Mars Ops Halted Due To 'Soft’ Short

Lee Rannals for redOrbit.com – Your Universe Online

NASA has suspended its rover Curiosity operations on Mars to check for possible causes of a voltage change detected this week. The space agency announced that engineers are investigating a “soft” short, which is a leak through a material that is partially conductive of electricity, rather than a hard short like one electrical wire contacting another.

“The vehicle is safe and stable, fully capable of operating in its present condition, but we are taking the precaution of investigating what may be a soft short,” said Mars Science Laboratory Project Manager Jim Erickson at NASA’s Jet Propulsion Laboratory, Pasadena, California.

The Curiosity team detected the soft short between the chassis and the 32-volt power bus that distributes electricity to systems throughout the rover. NASA received data on Sunday during Curiosity’s 456th Martian day, showing that the level had been about four volts, compared to the 11 volts it was on landing day.

Curiosity is designed to work throughout a range of voltages, a design feature called ‘floating bus.’ The rover had already experienced one soft short on landing day in August 2012, related to the explosive-release devices used for deployments shortly before and after the landing.

NASA said soft shorts can reduce the robustness of the system’s ability to tolerate other shorts in the future, and they can indicate a possible problem in the component in which the short occurred. The Curiosity team is planning on checking some of the possible causes for the voltage change. An analysis has shown that the change appeared intermittently three times during the hours before it became persistent.

The issue did not cause the rover to enter a safe-mode status, during which the activities would have automatically ceased pending further instructions. The space agency said that there is no indication that the issue is related to a computer reboot that triggered a safe-mode shut down earlier this month.

Curiosity put itself in safe-mode on November 7 for three days when an unexpected software reboot occurred during a communications pass with the Mars Reconnaissance Orbiter. The rover team analyzed data returned by the spacecraft to determine the root problem. They found that an error in existing onboard software resulted in an error in a catalog file. After determining this, the team was able to put the rover back online.

NASA has been testing the rover’s autonomous roll across the Martian landscape. Curiosity is able to choose a route by using its onboard computer to analyze stereo pictures that it takes during stops. In October the rover took its first two-day autonomous drive on the Red Planet, traveling a total of 260-feet all by itself.